1. Field of the Invention
This invention pertains to optical fiber switches for switching optical transmission paths. More particularly, this invention pertains to an optical switch having reduced back reflection.
2. Description of the Prior Art
Commonly assigned and copending U.S. patent application Ser. No. 300,205, filed Jan. 19, 1989 (a continuation-in-part of U.S patent application Ser. No. 191,014, filed May 6, 1989 now abandonment), teaches an optical switch. The switch is intended for use in the telecommunications industry for switching optical fibers that carry signal transmissions. The switch of the aforesaid patent application includes first and second pluralities of optical fibers bundled in first and second arrays. The two arrays are disposed facing one another, and rotatable about a common axis of rotation. By rotating one fiber array relative to the other fiber array, fibers of the opposing arrays may be selectively coupled or decoupled to provide switching.
In any optical fiber transmission system, it is desirable to design and construct the system to reduce or eliminate back reflection. Back reflection refers to the phenomenon where the signal-carrying light is partially reflected from the terminal end of an optical fiber back into the fiber. Back reflection commonly arises where the terminal end of the optical fiber is flat and orthogonal to the axis of the fiber and there is a refractive index discontinuity. With this geometry, a portion of the light passes through the terminal end. However, a noninsignificant insignificant portion of the light is reflected back into the fiber.
Recognizing the undesirable consequences resulting from back reflection, developers of optical transmission systems are commonly specifying limitations on the amount of back reflection which will be tolerated by optical fiber transmission equipment, such as optical switches. For example, common specifications may require that optical switches have less than about -40 dB back reflection.
It is an object of the present invention to improve upon prior optical switch design to reduce the back reflection associated with the switch.